Re: JDBC_FreeResult - Free resultset and preparedStatement

I wrote a simple java program and ran it under debugger. The debugger shows
that the ResultSet.getStatement returns a Statement object with object id
that that same as the PreparedStatement object. Hence closing it, caused
the PreparedStatement object to get closed also. The simple java program
also encountered sql Exception error when it attempted to use the
PreparedStatement object on the second execution.


"hockchai Lim" <lim.hock-chai@xxxxxxxxxxxxxxx> wrote in message
news:mailman.6352.1283964036.2619.rpg400-l@xxxxxxxxxxxxxxx

Hey Scott,
I commented out the JDBC_FreeResult(myRS) statemetn that is in my program
and tried to run the program again. This time it executed successfully
(including execution of the second call to this sub-proc). I'm a bit lost
on what the cause of problem is if it is not cause by JDBC_FreeResult
dealloacted the PreparedStatement.


"hockchai Lim" <lim.hock-chai@xxxxxxxxxxxxxxx> wrote in message
news:mailman.6344.1283963130.2619.rpg400-l@xxxxxxxxxxxxxxx

Thanks Scott, I must miss interpreted the code.

I'll dig more into the cause of the problem that I'm encountering below:

I've a sub-proc with code like this:
JDBC_SetLong(addressSelectPS(connIdx) :1 :piWGINTS.unii);
myRS = JDBC_ExecPrepQry(addressSelectPS(connIdx));
if myRS <> *null;
if jdbc_nextRow(myRS);
myRecExist = *on;
endif;
JDBC_FreeResult(myRS);
endif;


This sub-proc works fine on the first execution. But it get error below
when it is executed on the second time. The error happened when it
executes the JDBC_SetLong(addressSelectPS(connIdx) :1 :piWGINTS.unii).

java.lang.NullPointerException
at java.lang.Throwable.<init>(Throwable.java:181)
at java.lang.RuntimeException.<init>(RuntimeException.java:32)
at java.lang.NullPointerException.<init>(NullPointerException.java:36)
at com.mysql.jdbc.PreparedStatement.set(Unknown Source)
at com.mysql.jdbc.PreparedStatement.setLong(Unknown Source)


The RPG error (joblog) shows this:
Message ID . . . . . . : RNX0301 Severity . . . . . . . : 50
Message type . . . . . : Escape
Date sent . . . . . . : 09/08/10 Time sent . . . . . . :
11:16:58

Message . . . . : Java exception received when calling Java method.
Cause . . . . . : RPG procedure JDBC_SETLO in program SVCPGM/JDBCR4
received
Java exception "java.lang.NullPointerException:" when calling method
"setLong" with signature "(IJ)V" in class "java.sql.PreparedStatement".
Recovery . . . : Contact the person responsible for program
maintenance to
determine the cause of the problem.
Technical description . . . . . . . . : If the exception indicates that
the
Java class was not found, ensure the class for the method is in the
class
path. If the exception indicates that the Java method was not found,
check
the method name and signature. If the signature is not correct, change
the
RPG prototype for the method, or change the Java method, so that the
return
type and parameter types match. You can determine the signatures for all
the


"Scott Klement" <rpg400-l@xxxxxxxxxxxxxxxx> wrote in message
news:mailman.6320.1283960007.2619.rpg400-l@xxxxxxxxxxxxxxx

I don't agree with your assessment.

It closes the current statement -- i.e. it releases the database
resources it's currently using, so the database manager will stop
processing the SQL statement that you executed, and free up it's memory.

It doesn't free the PreparedStatement object you created! It doesn't
prevent you from inserting new parameter markers and running it again!
It just closes the previous run so you aren't running BOTH.


On 9/8/2010 9:51 AM, hockchai Lim wrote:

I just did some studying on Scott Klement's JDBC_FreeResult export
procedure. In observing the code, it seems like this procedure not
only
closes and frees the ResultSet, it also auto closes and frees the
PreparedStatement object that is associated to the ResultSet.

I've wrote a RPG program that needs to a same PreparedStatment object
to
perform different queries using different parameter mark values. So, I
really do not want to free the PreparedStatement object when freeing
the
ResultSet. Does anyone know of the best way to handle this?

Thanks